1. Field of the Invention
This invention relates to a novel intraluminal graft, stent, or conduit implant produced by demineralization of cortical bone having a lumen, appropriate shape and dimensions.
2. Background
In the field of vascular transplantation, many devices are known for opening an occluded vessel, as with a stent, or for replacing or strengthening portions of a vessel, as in bypass surgery. Various synthetic conduits for use in physiologic locations where production of a passage is desired have also been described. However, such methods typically depend on insertion into the biological milieu of a synthetic device, which typically requires removal at a later date, harvesting of autograft or allograft tissue from limited resource sites, or production of complex mixtures for preparation of the desired conduit or implant.
Examples of know methods for producing grafts, stents or conduits include the following:
A. Grafts
U.S. Pat. No. 5,376,110 discloses a chemically cross-linked collagenous graft material wherein physical force, stress or movement is applied during a collagen cross-linking process in order to derive desired shapes.
U.S. Pat. No. 5,192,311 discloses a method for making a homograft wherein a tubular substrate having a thrombogenic surface is implanted in a blood vessel in order to permit collagenous growth to occur on the thrombogenic surface to form a vessel which is then removed from the substrate and used as a graft material.
U.S. Pat. No. 4,787,900 discloses a method for making an inner layer of a multilayer blood vessel prosthesis by contacting collagen with an aminopolysaccharide and crosslinking the resulting polymer, and forming an outer layer by freeze-drying bioreplaceable material onto the inner layer.
U.S. Pat. No. 5,591,225 discloses an artificial blood vessel comprising a tube of a porous synthetic polymer on which a protein or peptide having cell adhesion and growth functions is covalently bonded to encourage cellular adhesion and to prevent thrombus formation.
U.S. Pat. No. 5,549,664 discloses an artificial blood vessel made from an elastomeric material wherein a first layer has closed, noncommunicating cells, and a second layer thereof has open, mutually communicating cells.
U.S. Pat. No. 5,037,377 discloses a method for improving the biocompatibility of a vascular graft by using collagen to coat a biocompatible fabric which is to be contacted with blood, and then cross-linking the collagen coating.
U.S. Pat. No. 3,284,557 discloses a method for "crimping" a tube of collagen for use as a vascular prosthesis, so that when bent, the collagen tube does not kink and thereby become occluded. The collagen tube was woven from "collagen yam".
B. Stents
U.S. Pat. No. 5,665,116 describes a method and apparatus for catheterization to dilate a vascular blockage wherein a catheter assembly carries a balloon to a site of vascular blockage where the balloon is expanded to uncoil a coiled ring structure having longitudinally extended struts, which is carried on the balloon, and which locks to remain in an uncoiled position to dilate the blocked vessel.
U.S. Pat. Nos. 5,195,984; 5,571,171; 4,776,337; and 5,102,417; disclose various embodiments of balloon catheters for insertion of stents.
C. Conduits
U.S. Pat. Nos. 4,963,146 and 5,026,381 disclose a multi-layered, semi-permeable conduit for nerve regeneration wherein the conduit is prepared by precipitation of an aqueous dispersion of Type 1 collagen and spinning the precipitate to form a conduit which must be further compressed, frozen, lyophilized, and cross-linked, prior to use.
U.S. Pat. No. 5,019,087 discloses a conduit prepared from Type 1 collagen and laminin for nerve regeneration, wherein the collagen and laminin are admixed at defined ratios.
D. Auxiliary Technology
U.S. Pat. Nos. 5,613,982 and 5,632,7798 disclose a method for reducing the immunogenicity of a collagenous implant by removing cells from a tissue to produce a tissue matrix, washing the tissue matrix to remove antigens, and treating with adhesion factors (fibronectin, heparin) to promote attachment of fibroblast cells immunologically acceptable to the intended recipient of the thus prepared implant.
U.S. Pat. No. 4,597,762 discloses a collagen preparation produced by proteolyzing mammalian Type-1 collagen containing material under specific conditions, cross-linking the proteolyzed material, reducing (bleaching) the cross-linked material and sterilizing the reduced material.
U.S. Pat. No. 5,507,813 discloses a shaped material derived from elongate, demineralized, bone particles having specified median lengths, and which are bonded to each other by admixture with adhesives, fillers, plasticizers, and the like.
U.S. Pat. No. 5,676,146 discloses a method for radiologic tracking of an implant, such as that described in U.S. Pat. No. 5,507,813, by including therein a piece of mineralized bone, which acts as a resorbable radiopaque marker.
U.S. Pat. No. 5,171,273 discloses a synthetic tendon comprising aligned, cross-linked, synthetic collagen fibers embedded in a non-crosslinked collagen matrix.
U.S. Pat. No. 4,923,380 discloses a method for preparing collagen tubes for use as a vascular prosthesis or nerve suture wherein aqueous collagen is "coagulated" as it is extruded in a tubular manner, followed by addition of azide, rather than glutaraldehyde, to induce "denaturation" of the collagen.
U.S. Pat. No. 5,139,505 discloses a radiopaque device comprising a collagen tube with frusto-conical ends and an intermediate annular rim for assisting in suturing adjacent hollow organs (intestines, bile ducts, etc.), along with a collagen wrap to be used as a band-aid.
In view of the above art in which various forms of grafts, stents, conduits and auxiliary technology has been described, it will now better be appreciated that the present invention provides a novel device and method for meeting the continuing need for grafts, stents and conduits for biological systems by providing partially or fully demineralized bone segments having a lumen for use in these applications. Any of the known technology, including the above mentioned auxiliary technology, however, may be applied in various embodiments of the present invention in order to, for example, reduce the immunogenicity or thrombogenicity of the present device, and the above discussed art is therefore incorporated by reference for that purpose.